Find 100th Derivative of f(x) = x/(1+x^2) at 1

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In summary, the task is to find the 100th derivative at 1 of f(x) = x/(1+x^2). The solution involves writing the function as a power series for |x| < 1 and using partial fractions. The roots of the partial fractions will be +/=i, and the series should converge for x=1.
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eok20
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Homework Statement


Find the 100th derivative at 1 of f(x) = x/(1+x^2)


Homework Equations





The Attempt at a Solution


For |x| < 1 I can write f as a power series (since 1/(1+x^2) = sum_n (-1)^n x^(2n)) but this won't work at 1. I tried writing out the first few derivatives at 1 explicitly but things got pretty messy. Any ideas?
 
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  • #2
Maybe I'm missing something but since this is a second-order equation, aren't all derivatives past the second one zero?
 
  • #3
Fleem, it is a fraction.

Hint: split it in partial fractions.
 
  • #4
Count Iblis said:
Fleem, it is a fraction.

Hint: split it in partial fractions.

I need glasses.
 
  • #5
eok20 said:

The Attempt at a Solution


For |x| < 1 I can write f as a power series (since 1/(1+x^2) = sum_n (-1)^n x^(2n)) but this won't work at 1. I tried writing out the first few derivatives at 1 explicitly but things got pretty messy. Any ideas?

Are you just trying to find the derivative at one point? If so, and you are trying to find the derivative at the point x=1, then why not do the power series at about x=1. If you use partial fractions as another poster suggested, the roots will be +/=i so I think the series should converge
 

FAQ: Find 100th Derivative of f(x) = x/(1+x^2) at 1

What is the 100th derivative of f(x) = x/(1+x^2) at 1?

The 100th derivative of f(x) = x/(1+x^2) at 1 is equal to 0.

How do you find the 100th derivative of f(x) = x/(1+x^2) at 1?

To find the 100th derivative of f(x) = x/(1+x^2) at 1, we can use the formula for the nth derivative of the quotient of two functions: (f/g)^n = (f^n - nf^(n-1)g + (n choose 2)f^(n-2)g^2 - ... - g^n)/(g^(n+1)).In this case, we have f(x) = x and g(x) = 1+x^2. Substituting these values into the formula gives us 0 as the 100th derivative at 1.

Is there a simpler way to find the 100th derivative of f(x) = x/(1+x^2) at 1?

Yes, there is a simpler way to find the 100th derivative of f(x) = x/(1+x^2) at 1. We can use the fact that the function is a rational function, which means that all of its derivatives will also be rational functions. Therefore, the 100th derivative at 1 will also be a rational function with a constant value of 0.

What does the 100th derivative of f(x) = x/(1+x^2) at 1 represent?

The 100th derivative of f(x) = x/(1+x^2) at 1 represents the rate of change of the function at x = 1, after taking 100 derivatives. Since the function is a rational function, its 100th derivative at 1 is 0, indicating that the rate of change is constant at this point.

Can the 100th derivative of f(x) = x/(1+x^2) at 1 be negative?

No, the 100th derivative of f(x) = x/(1+x^2) at 1 cannot be negative. As mentioned before, the function is a rational function and all of its derivatives will also be rational functions, which cannot have negative values. Therefore, the 100th derivative at 1 will always be 0.

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